Hepatitis A vaccine
|Target disease||Hepatitis A|
|Trade names||Havrix, Vaqta, Avaxim, Rixansart, Mevac-A|
|Main uses||Prevent hepatitis A|
|Side effects||Pain at site of injection|
|US NLM||Hepatitis A vaccine|
|(what is this?)|
Hepatitis A vaccine is a vaccine that prevents hepatitis A. It is effective in around 95% of cases and lasts for at least fifteen years and possibly a person's entire life. Two doses, 6 to 12 months apart, given after the age of one year provides long-term immunity. It is given by injection into a muscle.
The World Health Organization (WHO) recommends universal vaccination in areas where the disease is moderately common. Where the disease is very common, widespread vaccination is not recommended as all people typically develop immunity through infection during childhood. The Centers for Disease Control and Prevention (CDC) recommends vaccinating adults who are at high risk and all children. At risk groups recommended to have the vaccine include: certain occupations, close contacts with people with acute hepatitis A, men who have sex with men, people who use illicit drugs, people with chronic liver disease or blood clotting conditions, the homeless, and 2 to 4 weeks before travelling to areas were the disease is common.
Severe side effects are very rare. Pain at the site of injection occurs in about 15% of children and half of adults. Most hepatitis A vaccines contain inactivated virus while a few contain weakened virus. The ones with weakened virus are not recommended during pregnancy or in those with poor immune function. A few formulations combine hepatitis A with either hepatitis B or typhoid vaccine.
The first hepatitis A vaccine was approved in Europe in 1991, and the United States in 1995. The first dose, globally, was administered in 1992. It is on the World Health Organization's List of Essential Medicines. In the United States it costs US$50–100. In the UK, one dose of hepatitis A vaccine costs the NHS just over £20.
Within the U.S., the vaccine was phased in, around 1996, for children living in high-risk areas. In 1999, it was spread to areas with elevating levels of infection. In the U.S. as of 2007[update], the vaccine is strongly recommended for all children 12 to 23 months of age in an attempt to eradicate the virus nationwide. Although the original Food and Drug Administration (FDA) license for Havrix by GlaxoSmithKline is dated in 1995, it has been in use in Europe since 1993.
The U.S. Centers for Disease Control and Prevention (CDC), recommends vaccination of all children over one year of age, people whose sexual activity puts them at risk, people with chronic liver disease, people who are being treated with clotting factor concentrates, people working in close proximity to the virus, and people who are living in communities where an outbreak is present. Hepatitis A is the most common vaccine-preventable virus acquired during travel, so people traveling to places where the virus is common like the Indian subcontinent, Africa, Central America, South America, Asia, and Eastern Europe should be vaccinated.
The vaccine is given in the muscle of the upper arm, in two doses for the best protection. The initial dose of the vaccine should be followed up by a booster six to twelve months later. Protection against hepatitis A begins approximately two to four weeks after the initial vaccination. Protection lasts at least 15 years and is estimated to last at least 25 years if the booster is administered.
A Cochrane review found that both types of vaccines offer significant protection, for at least two years using the inactivated vaccine and at least five years with the attenuated vaccine. The review concluded that the inactivated vaccine is safe, but required more high quality evidence to assess the safety of the attenuated vaccine.[needs update]
Several commercial hepatitis A vaccines are available. The definition of (U)nits varies among manufacturers depending on how hepatitis A antigen is measured in their products.
- Avaxim: made by Sanofi Pasteur. Inactivated hepatitis A virus produced in MRC-5 cells. Each dose contains 160 U of antigen adsorbed on aluminium hydroxide (0.3 mg Al).
- Epaxal (no longer available): made by Crucell. Also sold under the brand names HAVpur and VIROHEP-A. This vaccine consists of virosomes, artificial particles composed of synthetic lipids and influenza proteins in addition to the hepatitis A antigen. It does not contain aluminium.
- Havrix: made by GlaxoSmithKline. Inactivated hepatitis A virus produced in MRC-5 cells. Each adult dose contains 1440 ELISA units of viral antigen adsorbed on aluminium hydroxide (0.5 mg Al). The pediatric (child) doses contain half the amount of viral antigen and aluminium.
- Healive: made by Sinovac. Inactivated hepatitis A virus cultured in human diploid cell, followed by harvest, purification, inactivation, and aluminium adsorption. Each adult dose contains 500 U of viral antigen. The pediatric dose contains 250 U of viral antigen.
- Vaqta: made by Merck. Inactivated hepatitis A virus produced in MRC-5 cells. An adult dose contains 50 U of antigen adsorbed onto 0.45 mg of aluminium (as aluminium hydroxyphosphate sulfate); a child dose contains half the amounts of antigen and aluminium.
- Biovac-A: made by Pukang, sold under the brand name Biovac-A in India and under the brand names Mevac-A in Guatemala, Philippines, Bangladesh, Nepal, Uzbekistan and Chile etc. It is a freeze-dried live attenuated hepatitis A vaccine. Hepatitis A virus H2 strain is produced in human diploid cells. A pack of 0.5ml vial of Biovac-A and 0.5ml ampoule of SWFI (sterile water for injection), contains not be less than 6.5 Lg CCID50. Only a single dose is needed. It is recommended by the WHO. Long term persistence research data predicated that sero-conversion remained and antibody titre was not less than 128 IU/ml, 15 years after vaccination.
- Hepatitis A and B vaccine is a vaccine against hepatitis A and hepatitis B.
- Hepatitis A and typhoid vaccine is a vaccine against hepatitis A and typhoid.
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